A chubby Gambino crime family soldier, following a code of mob justice, plotted to whack Salvatore “Sammy Bull” Gravano by tracking the underworld turncoat down in Arizona, authorities charged yesterday.

Thomas “Huck” Carbonaro was hit with a federal indictment last month for allegedly taking part in the 1998 execution-style murder of a too-talkative wiseguy.

But yesterday the NYPD, FBI and U.S. attorney’s office revealed that Carbonaro, 55, had been after much bigger game in 1999.

They said Carbonaro and unnamed others decided to murder Gravano, the informant who helped send John Gotti to jail for life, after discovering he had left the witness protection program.

Prosecutors said a conspiracy to kill Gravano was hatched after it was reported he was living “an open and conspicuous life in Arizona.”

Carbonaro felt responsible because he had been a member of Gravano’s mob crew – and according to the mob code of justice, it was expected of the members to exact revenge.

“It was their crew that had to mop up,” a law-enforcement source said.

Prosecutors said Carbonaro and others conspired to obtain two revolvers and a shotgun to carry out the hit.

But before they could track Gravano down to his home in a Phoenix suburb, the former underboss was headed back to jail after being charged in February 2000 with “ecstasy” trafficking. He is now serving 20 years.

Carbonaro, of Staten Island, is scheduled to be arraigned today on charges of murder conspiracy, gun possession and conspiracy to possess firearms in federal court in Brooklyn. He faces up to 20 years in jail if convicted.

He already faces a possible death penalty after being indicted April 17 on a wide range of racketeering charges – including the 1998 slaying of a suspected police informant outside a Staten Island strip club.

Carbonaro and a second Gambino soldier allegedly blew away Frank Hydell, a nephew of Danny Marino, the capo who had once been in line to succeed Gotti as head of the family.